In-depth analysis of interreader agreement and accuracy in categorical assessment of brown adipose tissue in (18)FDG-PET/CT

• DOI: 10.1016/j.ejrad.2017.03.012
• Publication Date: 2017-03-23T07:05:25Z
• Authors: Anton S. Becker; Caroline Zellweger; Khoschy Schawkat; Sanja Bogdanovic; Valerie Doan Phi van; Hannes W. Nagel; Christian Wolfrum; Irene A. Burger
• Keywords: Adult; Male; Observer Variation; 10042 Clinic for Diagnostic and Interventional Radiology; Reproducibility of Results; 610 Medicine & health; 10181 Clinic for Nuclear Medicine; Middle Aged; 03 medical and health sciences; 0302 clinical medicine; Adipose Tissue, Brown; ROC Curve; Fluorodeoxyglucose F18; Positron Emission Tomography Computed Tomography; 2741 Radiology, Nuclear Medicine and Imaging; Humans; Female; Radiopharmaceuticals; Retrospective Studies

To evaluate the interreader agreement of a three-tier craniocaudal grading system for brown fat activation and investigate the accuracy of the distinction between the three grades.After IRB approval, 340 cases were retrospectively selected from patients undergoing (18)FDG-PET/CT between 2007 and 2015 at our institution, with 85 cases in each grade and 85 controls with no active brown fat. Three readers evaluated all cases independently. Furthermore standardized uptake values (SUV) measurements were performed by two readers in a subset of 53 cases. Agreement between the readers was assessed with Cohen's Kappa (k), the concordance correlation coefficient (CCC) and the intraclass correlation coefficient (ICC). Accuracy was assessed with Bland-Altman and receiver operating characteristics (ROC) analysis. A Bonferroni-corrected two-tailed p<0.016 was considered statistically significant.Agreement for BAT grade was excellent by all three metrics with k=0.83-0.89, CCC=0.83-0.89 and ICC=0.91-0.94. Bland-Altman analysis revealed only slight average over- or underestimation (-0.01-0.14) with the majority of disagreements within one grade. ROC analysis yielded slightly less accurate classification between higher vs. lower grades (Area under the ROC curves 0.78-0.84 vs. 0.88-0.92) but no significant differences between readers. Agreement was also excellent for the maximum SUV and the total brown fat volume (k=0.90 and 0.94, CCC=0.93 and 0.99, ICC=0.96 and 0.99), but Bland-Altman plots revealed a tendency to underestimate activity by one of the readers.Grading the activation of brown fat by assessment of the most caudally activated depots results in excellent interreader agreement, comparable to SUV measurements.